This invention relates generally to gas turbine engines, and more particularly to an engine gas flow actuated seal and vane stop for a stator vane liner assembly.
Gas turbine engines typically include flowpath liners such as shrouds and stator vane liners which form an annular flowpath boundary for an engine working gas flow. Flowpath liners can be supported in an engine case structure, and can be segmented to accommodate differential thermal growth between the liner and the case structure. Seals are used between adjacent liners to restrict leakage of the engine gas flow between adjacent liners. Such leakage of the engine working flow reduces engine efficiency. In addition, leakage that impinges on the case can thermally damage the case, and leakage between the liners and the case can cause temperature gradients in the case which adversely affect rotor blade tip clearances. Where a case consists of two 180 degree halves bolted at a flanged horizontal splitline, sealing at the splitline is difficult, and leakage and impingement of the gas flow against the case flanges at the splitline is especially difficult to control.
U.S. Pat. No. 3,938,906 issued to Michel et al. disclose a slidable, spring loaded elongated seal 14 that extends in a tongue-in-groove manner from one turbine vane shroud to abut an end of an adjacent shroud. The mechanical spring is subject to failure due to mechanical fatigue, fretting, and wear in the hostile, high temperature environment of gas turbine engine, and adds complexity to the assembly. Further, any failure of the spring can result in loss of sealing and foreign object damage to downstream airfoils if broken spring pieces enter the engine working gas flow. The seal includes a retaining pin 18 and a slot 30 which can interrupt the sealing surface on seal 14 and provide a radial leakpath across the seal. A single seal member 34 for controlling axial flow leakage around the elongated seal 14 is disposed in radial slots 36 and 38 extending through the radial thicknesses of both the seal 14 and the shroud, thereby forming a continuous radial leakage path from the engine flowpath.
U.S. Pat. No. 2,833,463 issued to Morley shows blade rings 16 and stator blades 21 located circumferentially by washers secured by screws to the flanges of casing halves. The washers prevent motion of the stator blades 21 in the blade rings when the blades are acted on by the engine gas flow. Other designs can include stakes or ribs fixed to the case for preventing rotation of the blades in the blade rings or liners during engine operation. Such bolted or fixed attachments can introduce stress concentrations into the case structure.
FIG. 2 shows a known vane liner assembly with separate flexible spline seals extending between adjacent vane liners and seated in oppositely facing grooves in the adjacent vane liners. Separate seal pieces can become worn or break and enter the flowpath as foreign objects. U.S. Pat. No. 3,542,483 to Gagliardi shows two semicircular blade ring halves with axial and radial seal members extending between adjacent vane segments. However, in practice it is often not practical to include seals at the splitline between two 180 degree case halves. Simultaneous alignment of the grooves in the vane liners and the separate seals when the two case halves are being assembled is difficult, is labor intensive, and can result in damaged seals.